Characterization of photodiodes as transfer detector standards in the 120 nm to 600 nm spectral range

Using spectrally dispersed synchrotron radiation of continuously tuneable w avelength as delivered by the ultraviolet(UV) and vacuum ultraviolet (VUV) calibration facility of the Physikalisch-Technische Bundesanstalt (PTB) at the electron storage ring BESSY I in Berlin, various types of silicon photo diode have been examined for their radiometric performance in the 120 nm to 600 nm spectral range. Their absolute spectral responsivity was determined with a typical relative uncertainty of 0.7% using the synchrotron-radiatio n cryogenic electrical-substitution radiometer, SYRES, as primary detector standard. Particular emphasis has been given to the study of radiation-dama ge effects at wavelengths below 250 nm. In addition, the reflectance of the photodiodes was measured to determine their internal quantum efficiency. U sing a physical model for the internal losses, the mean energy to create an electron-hole pair in silicon was derived.